U.S. patent number 11,390,726 [Application Number 17/196,648] was granted by the patent office on 2022-07-19 for method of bonding perfluoroelastomeric materials to a surface.
This patent grant is currently assigned to Greene, Tweed Technologies, Inc.. The grantee listed for this patent is Greene, Tweed Technologies, Inc.. Invention is credited to Ronald R. Campbell, Christopher Corrado, Carmin Quartapella, Gary Reichl, Robert Anthony Rey, Brian Alan Ux.
United States Patent |
11,390,726 |
Campbell , et al. |
July 19, 2022 |
Method of bonding perfluoroelastomeric materials to a surface
Abstract
The invention includes a method of bonding a perfluoroelastomer
material to first surface that includes: (a) contacting a first
surface with a bonding agent comprising a curable perfluoropolymer
and a curing agent; (b) curing the bonding agent to form a
perfluoroelastomer material that is bonded to the first surface. In
the practice of such method, the bonding agent may be a solution
prepared by dissolving the curable perfluoroelastomer and the
curing agent in a solvent. In an embodiment of the invention, the
perfluoroelastomer material formed in step (b) is a coating layer
or, alternatively, the first surface is a surface of a
perfluoroelastomer member and the perfluoroelastomer material
formed is a perfluoroelastomer weld.
Inventors: |
Campbell; Ronald R.
(Harleysville, PA), Corrado; Christopher (Hatfield, PA),
Ux; Brian Alan (Red Hill, PA), Rey; Robert Anthony
(Schwenksville, PA), Reichl; Gary (Coopersville, PA),
Quartapella; Carmin (Schwenksville, PA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Greene, Tweed Technologies, Inc. |
Wilmington |
DE |
US |
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Assignee: |
Greene, Tweed Technologies,
Inc. (Wilmington, DE)
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Family
ID: |
1000006438856 |
Appl.
No.: |
17/196,648 |
Filed: |
March 9, 2021 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20210198447 A1 |
Jul 1, 2021 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14184809 |
Feb 20, 2014 |
10961369 |
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11970892 |
Jan 8, 2008 |
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60897651 |
Jan 26, 2007 |
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60897660 |
Jan 26, 2007 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C
65/7841 (20130101); C09J 127/20 (20130101); B29C
66/5261 (20130101); B29C 65/485 (20130101); B29C
65/4835 (20130101); B29C 66/742 (20130101); C08F
8/30 (20130101); B29C 66/1142 (20130101); C08K
3/36 (20130101); C08J 5/12 (20130101); B29C
66/71 (20130101); C09J 171/00 (20130101); C08F
8/30 (20130101); C08F 14/18 (20130101); B29C
65/1406 (20130101); B29C 66/5268 (20130101); C08J
2315/02 (20130101); B29C 65/14 (20130101); C08K
5/14 (20130101); B29C 65/526 (20130101); B29C
65/1412 (20130101); B29C 35/02 (20130101); B29L
2031/7096 (20130101); B29K 2027/18 (20130101); B29L
2031/06 (20130101); B29K 2019/00 (20130101); B29K
2305/12 (20130101); B29K 2027/12 (20130101); B29K
2305/02 (20130101); B29C 65/523 (20130101); B29C
65/52 (20130101); B29K 2995/0058 (20130101); B29L
2031/26 (20130101); B29C 65/5057 (20130101); B29C
65/522 (20130101); B29C 66/71 (20130101); B29K
2027/18 (20130101) |
Current International
Class: |
C08J
5/18 (20060101); C09J 171/00 (20060101); C09J
127/20 (20060101); C08J 5/12 (20060101); B29C
65/00 (20060101); B29C 65/48 (20060101); C08K
3/36 (20060101); C08F 8/30 (20060101); B29C
65/78 (20060101); B29C 65/50 (20060101); B29C
35/02 (20060101); C08K 5/14 (20060101); B29C
65/52 (20060101); B29C 65/14 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0303244 |
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EP |
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0399543 |
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EP |
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JP |
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JP |
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JP |
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JP |
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JP |
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H11102905 |
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JP |
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2001/064465 |
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JP |
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2005-220161 |
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JP |
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2010/516864 |
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May 2010 |
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JP |
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2000/008076 |
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Feb 2000 |
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WO |
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2003/076535 |
|
Sep 2003 |
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WO |
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2005/049746 |
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Jun 2005 |
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WO |
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2005/097890 |
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WO |
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2006/028906 |
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WO |
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2006/078425 |
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Jul 2006 |
|
WO |
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Other References
International Plastics Handbook, p. 54-55 published 1995. cited by
applicant .
Wang, Perfluoroelastomer and fluoroelastomer seals for
semiconductor wafer processing equipment, J. Fluorine Chem., 122
(2003) p. 113-119. cited by applicant.
|
Primary Examiner: Boyle; Robert C
Attorney, Agent or Firm: Calderone Bullock LLC
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of pending: U.S. patent
application Ser. No. 14/184,809, filed Feb. 20, 2014, and entitled
"Method of Bonding Perfluoroelastomeric Materials to a Surface",
which itself is a continuation of U.S. patent application Ser. No.
11/970,892, filed Jan. 8, 2008, entitled "Method of Bonding
Perfluoroelastomeric Materials to a Surface", which in turn claims
the benefit of priority under 35 U.S.C. .sctn. 119(e) to each of
U.S. Provisional Patent Application Nos. 60/897,660 and 60/897,651,
both filed Jan. 26, 2007, the contents of each of which are
incorporated herein by reference.
Claims
What is claimed is:
1. A method of forming a perfluoroelastomer coating comprising (a)
dissolving a curable perfluoropolymer, having at least one curesite
monomer comprising a cyano group, and a curing agent in a solvent
to form a solution, (b) applying the solution to a surface; and (c)
curing the perfluoropolymer to form a cured perfluoroelastomeric
coating on the surface, wherein step (c) comprises heating the
coating layer for a sufficient period of time to effectively cure
the perfluoropolymer, further wherein the curing agent is selected
from the group consisting of a monoamidine, a monoamidoxime and an
aryldioxime.
2. The method according to claim 1, wherein the curing step further
comprises heating the coating layer to about 149.degree. C.
(300.degree. F.).
3. The method according to claim 1, wherein step (a) further
comprises (i) forming a first solution of the curable
perfluoropolymer and a first solvent; (ii) forming a second
solution of the curing agent and a second solvent; and (iii)
combining the first solution and the second solution.
4. The method according to claim 3, wherein the first solvent and
the second solvent are identical.
5. The method according to claim 1, wherein step (b) comprises
spraying the solution onto the surface.
6. The method according to claim 1, wherein the curing agent is
perfluorooctanaidine or heptafluorobutyrlamidine.
7. The method according to claim 1, wherein the solution comprises
about 1% to about 25% by weight of the perfluoropolymer based on
the total weight of the solution.
8. The method according to claim 7, wherein the solution comprises
about 1% to about 10% by weight of the perfluoropolymer based on
the total weight of the solution.
9. The method according to claim 8, wherein the solution comprises
about 1% to about 5% by weight of the perfluoropolymer based on the
total weight of the solution.
10. The method according to claim 9, wherein the solution comprises
about 0.01% to about 5% by weight of the curing agent, based on the
total weight of the solution.
11. The method according to claim 10, wherein the solution
comprises about 0.01% to about 1.5% by weight of the curing agent
based on the total weight of the solution.
12. The method according to claim 11, wherein the solution
comprises about 0.25% to about 1% by weight of the curing agent
based upon total weight of the solution.
Description
BACKGROUND OF THE INVENTION
Perfluoroelastomers have readily been used to form various types of
O-rings or seals. Such seals are commonly manufactured by first
producing a complete mold for the seal in the desired seal
configuration and then compression molding a compound that includes
perfluoropolymers along with curing agents to form a completely
cured perfluoroelastomer seal or other part. However, with the
ever-increasing need for larger and larger seals or unusual
configurations, molding complete parts becomes more and more
expensive and less of an economical practicality. This is because
to form such parts requires not only the molds but also an
infrastructure sufficient to handle the large or unusually sized
molds, including presses and pumps related to molding
operations.
One approach developed to address this need has been to produce
seals from rod stock and splice the two rod stock ends together to
form the required size seal. Traditional splicing techniques have
not proven very successful with perfluoroelastomers. Splicing with
an adhesive provides a weak point in the seal that is prone to
attack because adhesives developed in the past generally do not
match the chemical resistance of perfluoroelastomers.
Methods of bonding a cured perfluoroelastomer to itself using a
thermoplastic perfluoropolymer bonding agent have been disclosed.
However, such processes result in fusing of the perfluoroelastomer
ends leading to an intermediate fusing layer i.e., a layer of fused
perfluoropolymer. This provides a non-homogenous section within the
perfluoroelastomer part i.e., the fused perfluoropolymer layer.
Thus, the fused perfluoropolymer could result in a "weak" point due
to increased susceptibility to chemical or physical attack,
increased compression set and reduced low temperature compliance
than the rest of the perfluoroelastomer seal material. There is,
therefore, a need in the art for an improved method of bonding
and/or welding perfluoroelastomers and parts formed from them that
is simple and economical and provides for a homogenous finished
part that substantially retains the strength of a solid finished
piece.
In addition to the challenges associated with joining
perfluoroelastomer surfaces, it is noted that perfluoroelastomers,
by virtue of the manner in which they are typically cured and
formed as noted above, and their unique vulcanization properties
(included physical and solubility properties) have not, however,
been successfully adopted for certain uses and applications in
which their chemical resistance and elastomeric properties would
otherwise be advantageous, such as in surface passivation or other
coating use.
Whereas attempts have been made to dissolve curable
perfluoropolymers in fluorinated solvents, such as, Fluorinert.RTM.
FC-40, FC-75 and FC-77 to try to prepare coatings, the resulting
coatings are typically not resistant to flow or to certain
solvents, because the coatings were not cross-linked. Attempts to
incorporate curatives, such as, organic peroxides with associated
co-curatives; such as, triallyl isocyanurate (TAIC), were
unsuccessful due to the poor solubility of such
hydrocarbon-containing curatives in the highly fluorinated solvents
needed to dissolve the uncured perfluoropolymer. Likewise,
bisphenyl-based curatives, such as bisaminophenol (BOAP) typically
also exhibit poor solubility in such highly fluorinated solvents
needed to dissolve perfluoropolymers curable with BOAP such as
those with cyano-group containing curesite monomers.
This lack of the ability to cure high molecular weight curable
perfluoropolymers in solution has restricted the use of
perfluoroelastomer coatings to non-critical applications where
"flow" of the uncured material is acceptable.
Attempts have been made to form perfluoroelastomer coatings in the
past, however, the uses and particular perfluoropolymer systems
formed into coatings are limited. U.S. Pat. No. 6,523,650 provides
one example of use of a perfluoroelastomer coating on an
electrostatic printing component as an outer coating. The patent
describes dissolving an elastomeric DuPont Kalrez.RTM.
perfluoroelastomer, derived from 3-phenoxypropylvinyl ether and at
least one fluorine-containing ethylenically unsaturated monomer, in
solvent and applying it as a coating. However, the patent does not
describe whether the perfluoroelastomer is in a cured state upon
dissolution and/or how the cure system is affected by
dissolution.
U.S. Pat. No. 5,268,002 teaches coating of pellicles for photomask
applications with a coating formed of a low molecular
perfluoroelastomer polymer that acts as an antireflective coat for
the pellicles. Such pellicles have a core layer of a polymer, such
as nitrocellulose, among others. The perfluoroelastomer polymers
include tetrafluoroethylene (TFE), perfluoroalkylvinyl ether (PAVE)
and a curesite monomer such as
perfluoro-(8-cyano-5-methyl-3.6-dioxa-1-octene) (8-CNVE). The
patent uses such polymers to form low molecular weight
perfluoroelastomers having these components by pyrolyzing the
elastomer noted above and then dissolving the low molecular weight
polymer in a fluorocarbon solvent such as Fluorinert.RTM. FC-40,
Fluorinert.RTM. FC-75 or Fluorinert.RTM. FC-77. The pyrolysis
enhances the solubility to enable the resulting materials to be
used in coating form. See also, U.S. Pat. No. 5,256,747.
Moreover, there is a need in the art for an easy-to-form surface
coating that can incorporate the advantages of a standard
perfluoroelastomeric coating (as opposed to a low molecular weight
coating), including allowing for use of a standard cure system and
final cured perfluoroelastomer compound without complex process
steps, while maintaining desired coating properties suitable for
use on process equipment and the like and a process for preparing
the same. The invention disclosed herein addresses this need and
the need for a method of perfluoroelastomer joining or splicing
disclosed above.
BRIEF SUMMARY OF THE INVENTION
Included within the several embodiments of the invention is a
method of bonding a perfluoroelastomer material to first surface
that includes: (a) contacting a first surface with a bonding agent
comprising a curable perfluoropolymer and a curing agent; and (b)
curing the bonding agent to form a perfluoroelastomer material that
is bonded to the first surface. In the practice of such method, the
bonding agent may be a solution prepared by dissolving the curable
perfluoroelastomer and the curing agent in a solvent. In an
embodiment of the invention, the perfluoroelastomer material formed
in step (b) is a coating layer or, alternatively, the first surface
is a surface of a perfluoroelastomer member and the
perfluoroelastomer material formed is a perfluoroelastomer
weld.
In one embodiment of the method, the first surface is a surface of
a perfluoroelastomer member, the bonding agent is also contacted to
a second surface and step (c) further includes curing the bonding
agent to form a perfluoroelastomer weld between the first surface
and the second surface. Upon curing, the perfluoroelastomer weld
includes essentially the same perfluoroelastomer as the
perfluoroelastomer member.
An embodiment of the invention also includes method of forming a
perfluoroelastomer coating that includes: (a) dissolving a curable
perfluoropolymer and a curing agent in a solvent to form a
solution, (b) applying the solution to a surface; and (c) curing
the perfluoropolymer to form a cured perfluoroelastomeric coating
on the surface. Additionally, coated substrates including a cured
perfluoroelastomer coating applied on at least one surface of the
substrate are also within the scope of the invention.
In another embodiment of the invention a method of bonding a
perfluoroelastomer member to a surface is disclosed. The method
includes (a) contacting a first surface of a perfluoroelastomer
member with a bonding agent comprising: a curable perfluoropolymer,
and a curing agent; (b) placing the bonding agent also in contact
with a second surface; and (c) curing the bonding agent to form a
perfluoroelastomer weld between the first and second surface,
wherein upon curing the perfluoroelastomer weld comprises
essentially the same perfluoroelastomer as the perfluoroelastomer
member.
In another embodiment, a method of bonding a perfluoroelastomer
seal to a gland is disclosed and includes placing a bonding agent
comprising a curable perfluoropolymer and curing agent within gaps
formed between a perfluoroelastomer seal and a gland; and curing
the bonding agent; wherein upon curing, the perfluoropolymer forms
essentially the same perfluoroelastomer as the perfluoroelastomer
seal.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a flowchart of a method embodiment of forming a
perfluoroelastomer coating;
FIG. 2 is an enlarged perspective for cross-sectional view of a
perfluoroelastomer coating made in accordance with an embodiment of
the present invention;
FIGS. 3a and 3b are perspective views of a conventional rod stock
material;
FIG. 4 is a perspective view of an embodiment of a splicing fixture
of the present invention;
FIG. 4a is a partial, enlarged, exploded side elevational view of
the rod stock material in FIG. 3a;
FIG. 4b is a partial cross-sectional view of the rod stock material
in FIG. 4a taken along line 4b-4b in FIG. 4;
FIG. 5 is a plan view of a perfluoroelastomer seal within a
gland;
FIG. 5a is a cross-sectional view of the perfluoroelastomer seal of
FIG. 5;
FIG. 6 is a flowchart of a method of bonding a
perfluoroelastomer;
FIG. 7 is a flowchart of a method of bonding a perfluoroelastomer
seal to a gland; and
FIG. 8 is large perfluoroelastomer seal made in accordance with an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Described herein are methods of bonding a perfluoroelastomer
material to first surface and, optionally, a second surface. Also
included are articles, such as seals and coated substrates that are
made using the methods. A perfluoroelastomer material, as used
herein, may be any cured elastomeric material derived by curing a
perfluoroelastomer (as defined herein) that includes a curable
perfluoropolymer having a crosslinking group to permit cure. A
perfluoroelastomer is substantially fluorinated, and preferably
completely fluorinated with respect to the carbon atoms on the
backbone of the perfluoropolymer. It will be understood that some
residual hydrogen may be present in perfluoroelastomers within the
crosslinks due to use of hydrogen in the functional crosslinking
group in some perfluoroelastomer formulations. In general,
perfluoroelastomers, once cured are used, for example, as
cross-linked polymeric formed articles such as seals.
The perfluoropolymers used to form perfluoroelastomer material upon
cure are themselves formed by polymerizing one or more
perfluorinated monomers, one of which is preferably a
perfluorinated curesite monomer having a functional group to permit
curing.
As used herein, a perfluoroelastomer is a polymeric composition
that includes a curable perfluoropolymer formed by polymerizing two
or more perfluorinated monomers, including at least one
perfluorinated monomer that has at least one functional group to
permit curing i.e., at least one curesite monomer. Such
perfluoroelastomer can include two or more of various
perfluorinated copolymers of at least one fluorine-containing
ethylenically unsaturated monomer, such as tetrafluoroethylene
(TFE), a perfluorinated olefin, such as hexafluoropropylene (HFP),
and a perfluoroalkylvinyl ether (PAVE) which includes alkyl groups
that are straight or branched and which include one or more ether
linkages, such as perfluoro(methyl vinyl ether), perfluoro(ethyl
vinyl ether), perfluoro(propyl vinyl ether) and similar compounds.
Useful examples of PAVEs include those described in U.S. Pat. No.
5,001,278, and in WO 00/08076, of which the disclosures related to
types of PAVEs are herein incorporated by reference. Other suitable
PAVEs are described, for example, in U.S. Pat. Nos. 5,696,189 and
4,983,697, of which the disclosures related to types of PAVEs are
also herein incorporated by reference.
Preferred perfluoropolymers are those which meet the industry
accepted definition of a perfluoroelastomer listed as an FFKM in
ASTM D-1418-05 and, are also preferably terpolymers or
tetrapolymers of TFE, PAVE, and at least one perfluorinated cure
site monomer which incorporates a functional group to permit
crosslinking of the terpolymer, at least one of which is a curesite
capable of being cured by the curatives described herein.
Preferred perfluoroelastomer polymers for use in the present
invention are either commercially available as curable
perfluoropolymers or are known to be manufactured and/or sold by
Daikin Industries, Inc., Solvay Solexis, Dyneon, E.I. Du Pont de
Nemours, Inc., Federal State Unitary Enterprise S.V. Lebedev
Institute of Synthetic Rubber in Russia, and Nippon Mektron in
Japan.
In an embodiment, the invention includes perfluoroelastomer
materials that are perfluoroelastomer coatings, and methods of
manufacturing such coatings, and perfluoroelastomer materials that
are welds acting to connect or splice a first surface to a second
surface.
Embodiments including these are formed, in part, by cure of a
perfluoroelastomer by a curing agent. Preferred are
peroxide-curable systems as well as cyano-curable systems. With
regard to peroxide-curable systems, preferred polymers include
terpolymers of TFE, PAVEs such as those described in U.S. Pat. No.
5,001,278 (incorporated herein in relevant part reference), and a
curesite monomer having a perfluorinated structure with a
peroxide-curable functional group including those known or to be
developed in the art, such as halogenated alkyl and other
derivatives, and partially- or fully-halogenated hydrocarbon
groups.
Regarding cyano-curable systems, most preferred are
perfluoropolymers as described in WO 00/08076, incorporated herein
by reference or other similar structures. The monomers in the
tetrapolymer of WO 00/08076 include tetrafluoroethylene,
perfluoromethylvinyl ether and two curesite monomers, a secondary
cyano curesite monomer,
CF.sub.2.dbd.CFO(CF.sub.2).sub.3OCF(CF.sub.3)CN and a primary cyano
curesite monomer,
CF.sub.2.dbd.CFOCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2CN. Preferred
compounds are those having a Mooney viscosity (measured at
100.degree. C. on a TechPro.RTM. viscTECH TPD-1585 viscometer) of
about 45 to about 95, and preferably of about 45 to about 65.
Primary curing agents for are peroxide-based cure systems may be
any known peroxide curing and co-curing agents known or to be
developed in the art, such as organic and dialkyl peroxides. For
the cyano-based polymers, preferred primary curing agents include
monoamidines and monoamidoximes as described as U.S. Patent
Publication No. US-2004-0214956-A1, the disclosure of which is
incorporated herein by reference in relevant part. While such
monoamidines and monoamidoximes are described as potential cure
accelerators or as curatives in the prior art, in the present
invention they are preferably used as primary curing agents.
The amidine-based and amidoxime-based materials include
monoamidines and monoamidoximes of the following formula (I)
described further below. Preferred monoamidines and monoamidoximes
may be represented by formula (I):
##STR00001##
wherein Y may be a substituted alkyl, alkoxy, aryl, aralkyl or
aralkoxy group or an unsubstituted or substituted fully or
partially halogenated alkyl, alkoxy, aryl, aralkyl or aralkoxy
group having from about 1 to about 22 carbon atoms. Y may also be,
and preferably is, a perfluoroalkyl, perfluoroalkoxy,
perfluoroaryl, perfluoroaralkyl or perfluoroaralkoxy group of from
1 to about 22 carbon atoms and more preferably a perfluoroalkyl or
perfluoroalkoxy group of from about 1 to about 12 carbon atoms, and
more preferably from 1 to 9 carbon atoms; and R.sup.1 may be
hydrogen or substituted or unsubstituted lower alkyl or alkoxy
groups of from one to about 6 carbon atoms, oxygen (such that
NHR.sup.1 is a NOH group) or an amino group. R.sup.2 may be
independently any of the groups listed above for R1 or hydroxyl.
Substituted groups for Y, R.sup.1 or R.sup.2 include, without
limitation, halogenated alkyl, perhalogenated alkyl, halogenated
alkoxy, perhalogenated alkoxy, thio, amine, imine, amide, imide,
halogen, carboxyl, sulfonyl, hydroxyl, and the like. If R.sup.1 and
R.sup.2 are both selected as oxygen and hydroxyl, such that there
are two NOH groups on the compound (a dioxime can be used), and in
that case, formula (I) can be further modified to accommodate a
dioxime formula in which the carbon atom and the Y group together
form an intervening aromatic ring and in which the NOH groups are
located ortho-, para- or meta- to one another on the ring, such as
with p-benzoquinonedioxime.
Preferred embodiments include those according to formula (I) in
which R.sup.2 is hydroxyl, hydrogen or substituted or unsubstituted
alkyl or alkoxy groups of from 1 to 6 carbon atoms, more preferably
hydroxyl or hydrogen. Also preferred are embodiments in which
R.sup.1 is hydrogen, oxygen, amino or a substituted or
unsubstituted lower alkyl of from 1 to 6 carbon atoms while R.sup.2
is hydrogen or hydroxyl. Most preferred are embodiments where
R.sup.1 and R.sup.2 are both hydrogen. Further preferred
embodiments include those in which Y is perfluoroalkyl,
perfluoroalkoxy, substituted or unsubstituted aryl groups and
substituted or unsubstituted halogenated aryl groups having the
chain lengths as noted above, particularly preferred are when
R.sup.1 and R.sup.2 are both hydrogen and Y is
CF.sub.3(CF.sub.2).sub.2-- (i.e., when the compound is
heptafluorobutyrlamidine) or a similar amidoxime compound.
Exemplary monoamidine-based and monoamidoxime-based curatives
according to formula (I) include perfluoroalkylamidines,
arylamidines, perfluoroalkylamidoximes, arylamidoximes and
perfluoroalkylamidrazones. Specific examples include
perfluorooctanamidine, heptafluorobutyrylamidine, benzamidine,
trifluoromethylbenzamidoxime, and trifluoromethoxylbenzamidoxime,
with heptafluorobutyrlamidine being most preferred. Curatives as
noted according to formula (I) may be used alone or in
combinations, such as in combinations of preferred and/or exemplary
compounds noted hereinabove or with secondary curatives.
The curatives according to formula (I) are preferably capable of
curing perfluoroelastomeric compositions, particularly those with
at least one cyano curesite monomer.
Other curative (curing agents) may include perfluoroelastomer
formulations can include bisphenols and their derivatives,
tetraphenyltin, triazine, peroxide-based curing systems (e.g.,
organic peroxides such as dialkyl peroxides), or combinations
thereof. Other suitable curing agents include oganometallic
compounds and the hydroxides thereof, especially organotin
compounds, including ally-, propargyl-, triphenyl- and allenyl tin,
curing agents containing amino groups such as diamines and diamine
carbamates, such as N,N'-dicinnamylidene-1,6-hexanediamine,
trimethylenediamine, cinnamylidene trimethylenediamine,
cinnamylidene ethylenediamine, and cinnamylidene
hexamethylenediamine, hexamethylenediamine carbamate,
bis(4-aminocyclohexly)methane carbamate, 1,3-diaminopropane
monocarbamate, ethylenediamine carbamate, trimethylenediamine
carbamate, bisaminothiophenols, bisamidoximes, and bisamidrazones.
Most preferably a peroxide cure system (including any necessary
co-agents) is used.
The curing system does not require, but may also optionally include
a variety of secondary curatives, such as bisphenyl-based curatives
and their derivatives, tetraphenyltin, triazine, peroxide-based
curing systems (e.g., organic peroxides such as dialkyl
peroxides)(if not used as a primary agent or if used in a
combination of peroxides, or combinations of these systems. Other
suitable secondary curing agents include oganometallic compounds
and the hydroxides thereof, especially organotin compounds,
including ally-, propargyl-, triphenyl- and allenyl tin, curing
agents containing amino groups such as diamines and diamine
carbamates, such as N,N'-dicinnamylidene-1,6-hexanediamine,
trimethylenediamine, cinnamylidene trimethylenediamine,
cinnamylidene ethylenediamine, and cinnamylidene
hexamethylenediamine, hexamethylenediamine carbamate,
bis(4-aminocyclohexly)methane carbamate, 1,3-diaminopropane
monocarbamate, ethylenediamine carbamate, trimethylenediamine
carbamate, and bisaminothiophenols.
Other optional additives for use with the various
perfluoroelastomer formulations can include the addition of fillers
such as graphite, carbon black, clay, silicon dioxide, polymeric
graphite, fluoropolymeric particulates (e.g., TFE homopolymer and
copolymer micropowders), barium sulfate, silica, titanium dioxide,
acid acceptors, cure accelerators, glass fibers, or polyaramid
fiber such as Kevlar.RTM., plasticizers, or other additives known
or to be developed in the perfluoroelastomeric art. However, it is
preferred for coating compositions used in semiconductor and other
particulate-sensitive applications, that such optional fillers not
be used, or that clean fillers (silica, barium sulfate or
fluoropolymer particulates) be used.
The bonding agent, which bonds to the first and/or to the second
surface (particularly for forming a weld-type connection), includes
a curable perfluoropolymer and a curing agent. The components of
the bonding agent may be individually dissolved and then combined
followed by an in situ curing cycle. However, it is also within the
scope of the invention to first compound the components and then
dissolve the compound in a solvent. Methods of compounding bonding
agent components may be according to any known technique in the art
or any to be developed and a detailed explanation of the
compounding and processing methods are not necessary for a complete
understanding of the present invention. For example, conventional
methods of compounding are described in International Plastics
Handbook, 3.sup.rd Edition, Saechtling, p. 54-55. However, it is
preferred that the primary individual components are each first
dissolved in a solvent(s) prior to combination.
In dissolving the components or formulation, the preferred solvent
for dissolution of the curable perfluoropolymer is a fluorosolvent
that is able to dissolve at least the curable perfluoropolymer
component, and more preferably, that is able to also dissolve the
curative(s). Solvents having the desired characteristics are known
in the art and include Fluorinert.RTM. FC-87, FC-84, FC-75, FC-77
and/or FC-43, commercially available from 3M and any similar
solvents. However, it should be understood that while such
fluorinated solvents are preferred, any solvent which is known or
to be developed, that is capable of dissolving the compounded
curable perfluoropolymer, and preferably the curative and/or the
primary components in the compounded perfluoroelastomer formulation
(i.e., the perfluoropolymer and the curative aside from any
additives) may be used within the scope of this invention.
Preferably the total amount of solvent to be used is about 70% to
about 95% by weight, more preferably about 90% to about 95% by
weight, and most preferably about 94% to about 95% by weight of the
finished solution prior to cure.
The curable perfluoropolymer is preferably present in a finished
solution in an amount about 1% to about 25% by weight, more
preferably about 1% to about 10% by weight, and most preferably
about 1% to about 5% by weight, based on the total weight of the
finished solution. The curing agent is preferably present in an
amount of about 0.01% to about 5%, more preferably about 0.01% to
about 1.5%, and most preferably about 0.25% to about 1% based upon
total weight of the finished solution prior to cure. It is
preferred that the weight percentage ratio of perfluoropolymer to
curing in the finished solution be about 30:1 to about 10:1, and
more preferably about 20:1.
In making the finished solution, the bonding agent may be initially
compounded to form a compounded bonding agent and then dissolved in
solvent in accordance with the above preferred percentages. In such
a method, the compounded flouropolymer might first be formed into
small pieces by, for example, a clicker die, although any other die
cutter, knife, scissor, or similar cutting apparatus suitable for
the intended use can be used. Preferably the pieces range from
about 0.010 inches to about 0.250 inches in size and more
preferably about 0.030 inches on average. The pieces can optionally
be ground into finer sized pieces. Preferably, the pieces are then
added to a solvent, such as those mentioned above, and then mixed.
Mixing the pieces in the presence of a solvent, for example on a
ball mill, facilitates the dissolution of the perfluoropolymer
formulation into the solvent.
More preferably, each of the primary components of the bonding
agent is first dissolved in solvent. In such a method, a first
solution (solution A) is formed by combining the curable
perfluoropolymer with a solvent in an aFmount of about 2 to about
50% by weight curable perfluoropolymer, more preferably 2 to 20% by
weight and most preferably 5 to 10% by weight based on the total
weight of the first solution. A separate solution (solution B) is
formed by combining the cure agents with a solvent in an amount of
about 0.02% to about 10%, more preferably about 0.02% to about 3%,
and most preferably about 0.50% to about 2% based on the total
weight of the second solution. Then the two solutions are
subsequently combined by taking equal parts of each solution and
combining them to achieve the desired percentage of the curable
perfluoropolymer and curative(s) in the finished solution. If
additives are used, they may be added in either of the two initial
solutions or in the finished solution in accordance with this
particular method.
In an embodiment where the bonding agent is applied to the surface
of a perfluoroelastomer member, the bonding agent of the present
embodiment is made using the same or substantially the same
perfluoroelastomer formulation as used to produce the rod stock to
which it is to be welded. In the present embodiment, the bonding
agent can include any of the compounded perfluoroelastomer
formulations as described above, which include a curative(s).
In an embodiment, the invention includes a method of bonding a
perfluoroelastomer material to a first surface by contacting a
first surface with a bonding agent comprising a curable
perfluoropolymer and a curing agent and curing the agent to form a
perfluoroelastomer material that is bonded to the first surface
such that the perfluoroelastomer material formed is a coating
layer. In such embodiments, the bonding agent may be a solution
that can be applied to a surface of a substrate by any number of
conventional means such as spray coating, dip coating, brushing,
layering, and the like. With reference to FIG. 2, a coated
substrate, generally referred to as 10, is formed by applying the
finished solution to an uncoated substrate 12. Once the bonding
agent solution is applied, it is cured in situ to form a coating
14. Once the substrate is coated a heat cycle is applied. The heat
cycle will vary depending upon the specific perfluoroelastomer
formulation used for the curing agent, however the heat cycle can
be configured to provide a sufficient amount of heat for a
sufficient amount of time to effectively cure the bonding agent.
Alternative curing can be used including ultraviolet, infrared or
other radiative curing methods as well as optional use of pressure.
While the invention should not be restricted to any specific cure
or cure cycle, it is preferred that heat is used at about
149.degree. C. (300.degree. F.) for about eight minutes. However,
the curing temperature will vary depending upon the type of
perfluoropolymer and curing agent used in the perfluoroelastomer
formulation. Such curing temperatures can range from about
138.degree. C. (280.degree. F.) to about 177.degree. C.
(350.degree. F.), and preferably about 149.degree. C. (300.degree.
F.) to about 177.degree. C. (350.degree. F.). One of ordinary skill
in the art will understand that curing conditions vary with
elastomer systems and that such temperature ranges are not intended
to be limiting with respect to the scope of the invention, since a
variety of perfluoroelastomer formulations can be used.
After heat curing, post curing may optionally, but not necessarily
be applied at about 180.degree. C. (356.degree. F.) or other
suitable post-cure temperature for about seven to eight hours or
other suitable cure cycle times, depending on the resulting
properties desired. An additional cool down time of one hour can
then optionally be applied.
Although the present embodiment has been described for coating a
single substrate, the process may also be used to bond two
substrates together as an adhesive or bonded layer formed in situ
between two opposing surfaces (not shown) such as in a laminated or
other multi-layered structure. It may also be used to bond on
three-dimensional, non-planar surfaces.
The application of the present embodiment is not limited to any
particular substrate surface type, but instead can be used to form
a perfluoroelastomer coating on any type of solid surface. Such
perfluoroelastomer coatings can be used to coat foamed materials,
metals, metal alloys, glass, elastomers, plastics, composites and
the like. As a result of the uniquely elastomeric and inert
character of such coatings, they have application in a wide variety
of areas, including, semiconductor processing parts, doors, and
equipment; surface passivation; handling or mechanical tools;
medical equipment and devices; automotive and aerospace parts and
surfaces, equipment subject to high corrosion (e.g., oil field and
catalytic process equipment) and the like. In addition, the
coatings as formed are highly chemically inert and insoluble.
The coatings may also be used to affect a seal in applications in
which the features are too small for conventional molded seal
parts, such as in "lab-on-a-chip" applications in which a very thin
silica or plastic layer must be sealed with a heat- and
chemically-resistant material. The material coatings may also be
used as sealants on metal surfaces such as those in aircraft engine
parts where in-service use conditions exceed the temperature range
for other elastomers such as nitriles or standard fluoroelastomers
(such as Viton.RTM.).
When pressures or temperatures exceed the capabilities of typical
elastomer seals, there are current uses involving metal-to-metal
seals. However, these seals must be highly polished to affect a
seal. It substantially increases the cost of forming such seals.
However, application of a thin coating as described herein on such
a substrate can affect a seal between metal parts using a less
polished and less expensive metal surface.
Such solutions and cured coatings can also be used to repair or
adhere to surfaces of expensive perfluoroelastomer molded parts
(such as O-rings, seals, gaskets and the like).
In an embodiment, the present invention provides for a method (as
illustrated in FIG. 6) of bonding perfluoroelastomer ("FFKM")
members, for example to form a seal (e.g., an O-ring or similar
shaped seal) out of rod stock. The term "rod stock" as used herein
means any preformed stock material, regardless of shape or
cross-sectional configuration that can be used to make a seal.
The rod stock 11, 20 (FIGS. 3a and 3b) is pre-formed using any
conventional molding process such as extrusion or compression
molding. Such molding processes are well known in the art and a
detailed explanation of them is not necessary for a complete
understanding of the present invention. During the pre-form
process, which is typically extrusion, some heat applied to the
mold at least partially cures the compounded perfluoroelastomer
formulation transforming the perfluoropolymer into at least
partially cured perfluoroelastomer. The remaining curing typically
occurs during post pre-form processes, such as press-molding or
oven post-cure.
With reference to FIGS. 3a and 3b, the perfluoroelastomer pre-form
or rod stock 11, 20 (as illustrated in FIGS. 3a and 3b) is
initially formed from a compounded perfluoroelastomer formulation.
Preferably the perfluoroelastomer rod stock 11, 20 is at least
about 25% to about 95% cured. Methods of compounding
perfluoroelastomer formulations may be according to any known
technique in the art or any to be developed and a detailed
explanation of the compounding and processing methods are not
necessary for a complete understanding of the present invention.
For example, conventional methods of compounding are described in
International Plastics Handbook, 3.sup.rd Edition, Saechtling, p.
54-55, the contents of which are incorporated herein.
The rod stock 11 has a first end 13a with a preferred
cross-sectional surface 15 in a shape which is generally circular.
The cross-sectional shape can alternatively be any other shape
consistent with the intended use such as an oval, square,
rectangle, or the like. The rod stock 11 also has a second end 13b
with a cross-sectional surface 15 with a generally circular
shape.
As used herein, the term "weld" is meant to broadly encompass any
joining together of two surfaces through use of a bonding agent
therebetween, whether in liquid or solid "plug" form, physically
and preferably using curable chemical crosslinking and/or bonding
between each of the two opposing surfaces to be welded and the
bonding agent, however, it should be understood that the two
opposing surfaces need not be formed of the same material. The
first end 13a of the rod stock 11 can be welded to the second end
13b of rod stock 11 to form a circular ring. Alternatively, the
first end 13a can be welded to a second rod stock 20 having ends
22a, 22b (as shown in FIG. 3a) which can be formed from the same
perfluoroelastomer formulation as rod stock 11. The weld for
joining various ends of perfluoroelastomer rod stock is formed by
coating or applying at least one end of the rod stock with a
bonding agent.
The bonding agent, either in the form of an extruded preform of the
perfluoroelastomer formulation to form a solid "plug" or in the
form of a solution of the compounded perfluoroelastomer formulation
is employed. As a solution, it is applied to the surface of the rod
stock 11. The bonding agent is then contacted with at least one of
the surfaces to be welded. It can be applied in liquid form as a
coating to a single surface such as 13a, or both opposing surfaces,
such as 13a, 13b or 22a, 22b, that are to be welded together. As a
solid "plug," it can be merely inserted between two surfaces to be
welded in a manner such that the plug will contact the surfaces
upon later curing and processing. As a plug, the preform is
situated next to, for example, a rod stock 11 surface, preferably
contacting the surface.
In operation, when using a bonding agent in solution to weld two
ends of perfluoroelastomer rod stock together, for example to form
an O-ring, at least one surface of one of the ends e.g., 13a is
initially coated with the bonding agent. The coating can be applied
by any number of conventional means such as spray coating, dip
coating, brushing, layering, and the like. The second end 13b of
the rod stock 11 may also optionally be coated with the bonding
agent when welding two ends of the same rod stock. The two ends of
the coated rod stock 13 are then placed in a fixture 30 (e.g., a
splicing fixture as shown in FIG. 4) to secure one end 13a adjacent
to or in contact with the second end 13b of the rod stock 10 (as
shown in FIG. 4a). The fixture 30 can be configured to accommodate
the rod stock 11 for size and alignment and to allow heat and
pressure to be exerted on the rod stock 11 to hold them in place
within the fixture 30. The heat and pressure are generally supplied
by a press, in which the fixture is mounted and operated. The
fixture 30 can optionally act to apply a heat cure cycle to the
bonding agent.
The fixture 30 includes a bottom portion 32 and a top portion 34.
The top 34 and bottom 32 portions include channels 36a, 36b
respectively for seating the rod stock material. A hinge 38
connects the top 34 and bottom 32 portions to allow the fixture 30
to open and close and to align the top and bottom portions of the
channel 36a, 36b.
After placing the coated rod stock 10 in the fixture 30, the
fixture 30 is closed and a heat cycle is applied. The heat cycle
will vary depending upon the specific perfluoroelastomer
formulation used for the curing agent, however the heat cycle can
be configured to provide a sufficient amount of heat for a
sufficient amount of time to effectively cure the bonding agent. An
effectively cured bonding agent is one that results in at least a
partially cured perfluoroelastomer (preferably one which is cured
greater than about 75%). The bonding agent is typically cured about
75% to about 95%, or up to about 99%. In the present embodiment,
the heat cycle includes heat of about 300.degree. F. for about 8
minutes. However, the curing temperature of the heat cycle will
vary depending upon the type of perfluoropolymer and curing agent
used in the perfluoroelastomer formulation and emeplay temperatures
are detailed above in the coatings context. One of ordinary skill
in the art will understand that curing conditions vary with
elastomer systems and that such temperature ranges are not intended
to be limiting with respect to the scope of the invention, since a
variety of perfluoroelastomer formulations can be used.
This heat cycle contributes to substantially if not fully
completing the cure reaction of the perfluoropolymer and curing
agent(s) within the bonding agent that subsequently results in the
same or substantially the same perfluoroelastomer as the
perfluoroelastomer of the rod stock. After the heat cycle, the
spliced ends can be post cured at about 180.degree. C. (356.degree.
F.) or other suitable post-cure temperature for about seven to
eight hours or other suitable cure cycle times. An additional cool
down time of one hour can then optionally be applied. Preferably
the bonding agent forming the perfluoroelastomer splice is cured to
about 95% as noted above. In addition to heat cure cycles, it is
also within the scope of the invention to use infrared, UV, or
other radiative curing techniques.
This welding process can be applied to a variety of rods having
multiple ends to form a variety of sealing rings of varying sizes,
shapes, and configurations. The resulting seals, which can be very
large in size, have a cured, indistinguishable, and homogenous
weld(s) compared to seals wholly formed from a single-step mold
operation. That is, the perfluoroelastomer weld has the same or
substantially the same chemical composition as the
perfluoroelastomer rod stock. This advantageously results in the
seal having the same highly resistant chemical composition
throughout. Thus, there are no weak points or welded ends that are
more vulnerable to chemical and/or physical attack than the rod
stock bulk seal material.
Although the present embodiment has been described for bonding two
surfaces of the same rod stock or two different pieces of rod stock
made from the same perfluoroelastomer, the present invention is not
limited to bonding such materials only. The present invention can
also be used to weld two different pieces of rod stock made from
different perfluoroelastomers, such as any of the
perfluoroelastomers described above. Further, the invention can be
used to bond or weld various other types of perfluoroelastomers
surfaces not in rod form--in sheet form, molded form, lamination
form and various other shapes.
In another embodiment, the present invention provides for a method
of potting a perfluoroelastomer seal 40 as illustrated in FIGS. 5
and 7 using a bonding agent as described in any of the above
embodiments. As used herein and shown in FIG. 5a, the term
"potting" means filling in of gaps 42 or spaces between a seal 40
and a seal gland 44. The seal gland 44 is typically formed from
materials that are highly resistant to chemical attack such as
aluminum and stainless steel. In this embodiment, the bonding agent
is placed within the gaps 42 between the seal 40 and the seal gland
44. After potting the bonding agent, the entire construct i.e., the
seal 40, seal gland 44, and potted bonding agent, is heated to
about 149.degree. C. (300.degree. F.) for about eight minutes. The
heat cures the bonding agent and as a result forms a
perfluoroelastomer bond between the seal 40 and the seal gland 44.
An advantage of the present embodiment is that the
perfluoroelastomer seal 40 then is securely bonded to the seal
gland 44 which advantageously lowers particulation or degradation
of the primary sealing material due to the additional
perfluoroelastomer from the weld and because there is then
minimized gapping between the seal 40 and the gland through which
particulation may migrate. In addition, the bond eliminates the
relative motion and hence abrasion, between the seal and gland,
further contributing to lower particulation.
The application of the present embodiment is not limited to potting
such as seal against a gland having any particular composition, but
instead can be used to pot a perfluoroelastomer seal on a variety
of gland surfaces, for example, formed of metals, metal alloys,
plastics, composites and the like. However, metallic and metallic
alloy surfaces are most typically encountered in such applications
of use. Such potting uses can be used in various bonded gland
applications, including, semiconductor doors, gates, and other
pre-bonded surface sealing applications, and are particularly
useful when such applications are subject to high corrosion such as
semiconductor manufacturing conditions.
Example 1
In this example, a large perfluoroelastomer seal was made using
Chemraz.RTM. molded subsections which had been cured, but not
post-cured. One section was rectangular in configuration, wherein
the rectangle had rounded corners. Two other circular sections were
prepared. The rectangular section was sliced transversely across
the long-sided portions of the rectangle. After cutting, two
half-rectangular end pieces were formed. The circular sections were
then sliced so as to form a rod, and shortened to the appropriate
length to form two straight sections of desired length. The
resultant two rectangular end pieces were joined to the two
straight sections using a bonding agent and a splicing fixture to
form a resultant part having the shape shown in FIG. 8.
The bonding agent used was prepared by first compounding a
perfluoroelastomer formulation having the following constituents,
as noted in parts by weight:
TABLE-US-00001 Components Parts by Weight Curable Perfluoropolymer
100 Silica 9 Peroxide-Based Curing Agent 1.5 Peroxide-Based Cure
System Co-Agent 4 Barium Sulfate 32
After compounding, the compounded formulation was cut into small
pieces, approximately 0.25 inches in size in the largest dimension
using a die cutter. The pieces were then added to ajar having
Fluorinert.RTM. FC-77 solvent. The solvent was added so as to
make-up 94% by weight of the total solution. The jar was then
placed on ajar mill and continuously rolled for about forty-eight
hours to form the bonding agent.
The bonding agent was coated on one end of a first rod stock member
and placed within a sealing fixture such as that shown in FIG. 4,
to be welded to a second rod stock member. The second rod stock
member was also coated and placed so that its end was pressed
against the coated end of the first rod stock member. The sealing
fixture was then closed and heated to about 149.degree. C.
(300.degree. F.) for about eight minutes to cure the bonding agent.
This welding process was performed four times at each desired weld
to form the finished part and to create the welds to form a
large-formed seal. The overall rectangular dimensions of the
finished part as shown in FIG. 8 were approximately 2.1 meters
long.times.0.17 m wide with a transverse cross-sectional diameter
(being generally circular in transverse configuration) of about 0.6
cm (the shape formed at the weld was not perfectly round, but was
very close). The part was then post-cured at 180.degree. C.
(356.degree. F.) for 7.25 hours followed by a one hour cool down
period.
Example 2
A perfluoroelastomer coating was made by forming a first solution
(Solution A). Solution A was formed by dissolving 100 parts by
weight of a curable cyano-curable perfluoropolymer prepared in
accordance with WO 00/08076 (a perfluoroelastomer gum having a
primary and secondary cyano curesite) in 900 parts by weight of
Fluorinert.RTM. FC-43 fluid solvent from 3M. A second solution
(Solution B) was made by dissolving 5 parts by weight of
heptafluorobutyrlamidine as a curing agent in 995 parts by weight
of the same solvent used to form Solution A. Solutions A and B were
then combined in equal parts by weight to form a finished coating
solution. The finished coating solution was applied on a metallic
substrate surface and subjected to a heat curing cycle of
100.degree. C. (212.degree. F.) for about four hours. The resulting
cured perfluoroelastomer coating was clear. Similar coatings were
also prepared on glass, plastic and synthetic rubber.
* * * * *